1. Field of the Invention
The present invention relates to missiles. More specifically, the present invention relates to harness assemblies for electrically joining various sections of high performance missile systems.
2. Description of the Related Art
High performance missile assemblies generally include a plurality of different sections that, when secured end-to-end, form the missile fuselage. Normally, a guidance section is mounted forward of the propulsion and warhead sections with a control section mounted to the rear of the propulsion and warhead sections. In order to electrically interconnect the guidance and control sections, a conventional wire harness is employed. Because it is not possible to run such a harness internally through the propulsion and warhead sections of such a missile fuselage, the harness is mounted outside the missile adjacent the exterior surface. A conventional wire harness assembly is comprised of discrete electrical lines individually insulated from the external environment. In one such known assembly, the individual wires are assembled with plastic tie-wraps and are wire mesh overbraided for EMI protection. To provide additional protection against the environment, the harness wires may be positioned within a protective sleeve to insulate against severe aerodynamic exposure.
Each discrete electrical wire forming a conventional harness is individually connected at opposite ends to a receptacle extending from one of spaced-apart missile sections and then potted with silicon to seal the connection against environmental penetration and degradation. During final assembly, the electrical harness is secured to the missile airframe by metal clamps and adapters. A harness cover is then mounted over the electrical harness and secured to the missile fuselage with attachment fasteners. The electrical harness cover serves to protect the harness wires while providing the missile with aerodynamic form factoring, aeroheating and impact load insulation. If necessary, the harness cover may also provide additional EMI protection.
In any event, the process of connecting each wire to its receptacle and then mounting the cover over the harness has been found to be labor intensive, prone to human assembly error and susceptible to handling damage.
Hence, a need exists in the art for an improved electrical interconnection assembly that functionally connects various missile sections to one another notwithstanding a location of certain sections on opposite sides of warhead and/or propulsion sections. The electrical interconnection assembly should utilize advanced manufacturing and assembly techniques. The interconnection assembly should be packaged to withstand and operate in the extremely adverse environments, both temperature and pressure, routinely encountered by the missile during flight to the target.
The present invention addresses the need in the art for an improved electrical interconnection between various sections forming a missile fuselage. The invention includes an electrical interconnection assembly integrally formed within and surrounded by a protective housing shaped as an aerodynamic fairing and adaptable for attachment to an exterior surface of the missile fuselage. The protective housing also includes pre-stressed structural foam surrounding the interconnection members for added insulation. The interconnection assembly and the surrounding protective housing are fabricated as a single, composite member. The electrical interconnection assembly is sealed from ambient atmospheric humidity, shielded from Electro-magnetic Interference (EMI) and insulated from aerothermal heating by the external housing which is formed as a laminate structure.
The electrical interconnection assembly may consist of a plurality of separate electrical connecting members, each embedded directly into the laminate before it is molded into the aerodynamically-shaped protective housing or fairing. This eliminates the need for conventional harness insulating techniques such as Teflon bagging, manual hardware mounting and cable strapping. Preferably, an embedded mesh screen is formed as the housing is created and functions to envelop the electrical interconnection members to provide additional EMI shielding while at the same time being grounded to fasteners retaining the housing in position against the outer surface of the missile. The pre-compressed structural foam surrounding the interconnection members serves to insulate the members from aerodynamic heating. The foam flows within the housing during cure so that the laminate can conform to the mold shape. The foam forms a lightweight sandwich core to enhance laminate stiffness and strength.
The protective housing or fairing may be formed of a resin material such as Cyanate Ester. Alternatively, the housing may be molded from fiber reinforced Bismaleimide (BMI) resins which, along with Cyanate Ester, are known for their high temperature airframe applications as well as their economical cost of production. BMI laminates have been tested for jet engine firewall applications at over 2000xc2x0 F., and have been found to degrade in a predictable, graceful manner without catastrophic failure over a period of approximately fifteen (15) minutes. BMI is as processible as epoxy, has thermal capabilities approaching that of polyimides, yet has no carcinogenic downside. BMI enables utilization of automated fabrication techniques such as filament winding, compression molding and Resin Transfer Molding (RTM) in manufacturing complex composite housing assemblies in a cost effective manner.
Large combinations of electrical wires, cables, and bundles may compromise the integral housing assembly process, therefore designs utilizing higher density cabling should be attempted. Alternatively, printed wiring, ribbon cable, and/or polyurethane flex cables may serve as the electrical interconnection members. Once the composite interconnection assembly and protective housing is positioned adjacent the outer surface of the missile, fixed or floating connectors extending from receptacles mounted on the various sections of the missile could plug into connectors integrally formed with the housing, thereby eliminating the need for silicon potting.
A primary goal of the present invention is to be able to produce generic airframe electrical interconnections that are applicable to multiple missile production lines, at a significantly reduced cost compared to existing interconnection assemblies. The aerodynamically-shaped housing may take any desired shape, for example, a fin attachment member or an elongated, beam shaped fairing. In any case, the composite housing will consist of a Glass/BMI laminate containing either pre-compressed structural or high temperature syntatic foam, copper EMI mesh, Kapton and/or polyurethane flex cables sandwiched with a molded in-place electrical connector adaptable for connection to various sections of the missile.